You have mentioned you can see boot option as BIOS/EFI , this means your client machine has support for BIOS and UEFI both ; If your client machine is using EFI as boot option then booting of this client machine to PXE will fail because DS 7.1 does not support UEFI PXE boot.

Go to setup and check boot option if EFI is enabled and configured for boot , then change this to BIOS and reboot the client machine again.

Yogesh Sadhu.

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